Review of the Prior Art
Many load-bearing articles are supported on frames made of tubular metal; the fabric seats of wheelchairs and of lawn and beach furniture are common examples. It often occurs that the load-bearing article, i.e., the wheelchair seat, wears out and requires replacement. Typically, wheelchair seats are made principally of fabric and are mounted to the tubular metal wheelchair frames by sheet metal screws which are passed through grommets formed around suitable holes in the margins of the chair seat. Repairs to wheelchairs, either by the user of the wheelchair or by others, is often frustrated and made very difficult, if not impossible, where the screw holes in the chair frame are stripped. In fact, stripping of the holes may be the principal cause for the repair in that the seat itself may be sound, but the connection of the seat to the chair frame may not be sound due to one or more of several causative factors including the load applied to the chair seat, and the fact that the tubular metal chair frame is relatively thin walled. The result of these causative factors is that the screws used to secure wheelchair seats frequently strip out of the holes provided for them in the chair frame.
Where the screw-receiving hole in a wheelchair frame is stripped or is otherwise oversized relative to the screw, commercially available screw anchors may not conveniently be used. If commercially available anchors are to be used, the screw hole must be further enlarged simply to permit the anchor to be inserted into the hole. Enlargement of the screw holes in wheelchair frames is undesirable because such practice leads to weakening of the chair frame and also requires the use of special equipment, such as a power drill, which is usually not accessible to the person desiring to make the repair at the time the repair needs to be made. Further, commercially available screw anchors are relatively long and cannot be used in modern wheelchair frames. The substitution of a nut and bolt in place of a sheet metal screw is impractical unless a hole is drilled entirely through the tubular frame, and this is not desirable for the reasons noted above.
The problem to which this invention is addressed was initially discerned in the context of my desire to make repairs to a wheelchair. It will be apparent, however, that the anchor of the present invention is useful in a variety of situations and is not restricted in use only to the making of repairs to wheelchairs.
In the preparation of this patent application, the following U.S. patents were specifically considered, U.S. Pat. Nos.:
394,537 PA1 1,295,589 PA1 1,295,590 PA1 1,340,778 PA1 1,364,298 PA1 1,801,505 PA1 1,881,836 PA1 2,258,860 PA1 2,259,720 PA1 2,561,679 PA1 2,588,860 PA1 2,990,866 PA1 3,148,579 PA1 3,189,075 PA1 3,221,790 PA1 3,921,280 PA1 3,962,744
Swiss Pat. No. 295,595 was also considered.
The several devices shown in Swiss Pat. No. 295,595 are intended for use as anchors in holes formed in stone or masonry, and cannot realistically be used to serve the purposes addressed by the present anchors. The assemblies shown in U.S. Pat. No. 2,259,720 are designed for incorporation into new products which must be shaped accordingly; these arrangements cannot be used to make repairs in existing products which were not originally made with the necessary features. The rail tie anchor shown in U.S. Pat. Nos. 1,295,589 and 1,295,590 require two-handed operation as they must be held secure from rotation relative to the bolts with which they are used as the bolts are installed. The washer component of the lock nut assembly illustrated in U.S. Pat. No. 394,537 is used, in effect, as a key between a specially configured bolt and a form of castle nut and, thus, has only superficial similarity to certain forms of the present anchor.
A device addressed to the problems described above should be inexpensive, simple, easy to use, require only standard tools to use, and be capable of use by a single person using one hand to drive the fastener, thereby leaving the other hand free to hold one of the two things being connected together.